212 rare osteoarthritis: ochronosis and kashin-beck disease1768 rare osteoarthritis: ochronosis and...

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Rare osteoarthritis: ochronosis and Kashin-Beck diseaseVirginia Byers Kraus

212 normally retained in the body because of its high renal clearance6; the absence of the HGD enzyme leads to abundant urinary excretion of homogentisic acid, which darkens slowly upon oxidation by prolonged exposure to air. The darkening is hastened by the addition of alkali to the urine and is reflected in the original term for homogentisic acid, alkapton, which refers to its avidity for alkali. The distinctiveness of alkaptonuria accounts for reports of dark urine, including urine “as black as ink,” dating as far back as the Middle Ages.2 There has even been biochemical confirmation that ochronotic pigment in the bone and articular hip cartilage of an Egyptian mummy originated from homogentisic acid, which demonstrates that this disorder has afflicted humans since ancient times.7

EPIDEMIOLOGYAlkaptonuria or ochronosis is one of the rare diseases that affect human beings on a worldwide scale.8 In the United States, alkaptonuria has a prevalence of 1 case per 250,000 to 1 million live births.9 The highest frequen-cies are reported in Slovakia and the Dominican Republic, in which the prevalence approaches 1 case per 19,000 inhabitants,10 and in a single village in southern Jordan with a large number of cases (40 individuals in 17 families) considered a probable consequence of the high rates of consanguineous marriages in Jordan.11

CLINICAL FEATURESPatients with ochronosis are distinguished by the triad of dark urine on addition of alkali, ochronotic pigmentation, and arthritis.12 Alkaptonuria is present at birth and is often diagnosed by discoloration of the diapers. This is the only sign of the disorder in the pediatric age group,13 and many patients remain undiagnosed until adulthood because 25% do not have the characteristic dark urine staining.14 It is possible that many of the early manifestations of this disorder may go unnoticed by the patient, including dark urine and dark cerumen at birth, axillary pigmentation at puberty, and earlobe skin and scleral pigmentation at 20 to 40 years of age.15 Cases that escape detection in childhood are usually diagnosed on the basis of chronic joint pain, which typically develops in the third decade of life.3 The delay in appearance of the ochronotic arthropathy until after midlife is often ascribed to a waning efficiency of the renal clearance of homogentisic acid, leading to an accelerated accumulation of homogentisic acid oxidation byproducts with aging.16

The arthropathy that develops affects the spine and large joints. The low back is frequently the signal anatomic site. The spine involvement resembles ankylosing spondylitis but differs in sparing the sacroiliac joints.3 The pattern of spine involvement is reported to differ from typical OA in that thoracolumbar changes predominate rather than lumbosacral degeneration,16 although the severity of lumbar spine involvement had the strongest correlation with disability measures in a study of 53 patients.17 Narrowing and dense, wafer-like calcification of the intervertebral disks are the most characteristic findings in the spine (Fig. 212.3), and osteophytes are said to be usually absent or of small size.18,19 The peripheral arthritis closely resembles that of OA; however, the hands and feet are usually spared.19 Arthritis of the peripheral joints is generally observed about 10 years after spinal changes (Fig. 212.4). The main differences among ochronotic arthropathy, primary OA, and ankylosing spondylitis are summarized in Table 212.1. Tendon involvement is typically symmetric and involves traction tendons and their insertion sites with characteristic changes of enthesopathy, in general sparing tendons with synovial sheaths.20 Tendon and ligament ruptures are reported to occur with minimal provocation.3,21 Pain, stiffness, crepitation, flexion contractures, and limitation of motion are the most common clinical features.19 Loose (osteochondral) bodies may cause joint-locking episodes.19 Synovial effusions are reported in about half of cases, with cell counts of 100 to 700 cells/mm3 and a predominance of mononuclear cells.16,19

Increased bone resorption and osteoporosis have also been documented in association with ochronosis, even in the absence of immobility.22 Other disease manifestations include renal and prostate stones, aortic valve

INTRODUCTIONOsteoarthritis (OA) comprises a heterogeneous group of joint diseases, some of common and some of rare occurrence. Although the rare forms discussed here impact individuals infrequently or in specific and circumscribed geo-graphic regions, nevertheless an understanding of these rare forms of OA may provide useful insights into the nature and pathogenesis of the more common varieties of OA.1 (Other rare hereditary disorders of cartilage and bone, some of which can lead to OA, are described in Chapter 215.) These rare forms of OA are thought to derive from diverse causes that include genetic determinants (ochronosis) and a combination of genetic, nutritional, and biogeochemical factors (Kashin-Beck disease [KBD]). This diversity of causes is itself illustrative of the multiple pathways to the syndrome of joint failure that we recognize as OA. Although each of these diseases presents clinically as a form of OA, there are differentiating manifestations by which these arthropathies can be distinguished from one another. An appreciation of these subtleties is key to the recognition and management of these disorders.

OCHRONOSIS

HISTORYOchronosis and alkaptonuria are two names that refer to different manifestations of the same condition resulting from an inborn error of tyrosine metabolism—a deficiency of the enzyme homogentisate 1,2-dioxygenase (HGD, also known as homogentisate oxidase, or HGO) (Fig. 212.1). The connection between these two entities was recognized by Albrecht in 1902.2 Simultaneously, this was the first human disorder found to conform to the principles of mendelian autosomal recessive inheritance.3 In 1908, the term inborn errors of metabolism was first coined by Archibald Garrod to describe this and three other diseases.4 The absence of the HGD enzyme, normally highly expressed in hepatocytes,5 leads to the accumulation of metabolites of homogentisic acid in the connective tissues of individuals who are affected; this deposition causes an ochre-like pigmentation in the skin, sclera, and cartilages of the body (Fig. 212.2) and is the characteristic for which the disease was named ochronosis by Virchow. Only a small proportion of the homogentisic acid formed endogenously is

Key PointsOCHRONOSIS■ Ochronosis is a rare autosomal recessive disorder resulting from a constitutional lack

of homogentisic acid oxidase.

■ In ochronosis, homogentisic acid undergoes autoxidation as well as enzymatic oxidation and polymerization to form an ochronotic pigment that accumulates in cartilage and connective tissues.

■ The endogenous form of ochronosis may be confused with exogenous ochronosis, a limited hyperpigmentation of skin caused by various drugs and chemicals.

■ Clinical features of ochronosis include homogentisic aciduria, pigmentation of cartilages and other connective tissues, and in later years, generalized osteoarthritis of the spine and large joints, termed ochronotic arthropathies.

KASHIN-BECK DISEASE■ Kashin-Beck disease (KBD) is a severe, progressive osteoarthropathy of unknown

cause endemic to China and Tibet, with onset in childhood.

■ Three interacting causal mechanisms have been proposed, including a deficiency in trace elements (selenium and iodine), exposure to organic matter in contaminated drinking water, and contamination of food by noxious fungal and bacterial toxins.

■ The disease is characterized by necrosis and remodeling of cartilage, including growth plates.

■ Clinical features of KBD include generalized osteoarthropathy involving the ankles, knees, interphalangeal joints, wrists, and elbows with foreshortened phalanges; more severe involvement of distal and lower limbs; and an association with short stature.

CHAPTER 212 Rare osteoarthritis: ochronosis and Kashin-Beck disease 1769

X

HO CH2

HO OH

OH

O O

HO CH2 OH

H2N O

OH

H2CO

HO OH

OH–

OH

OH

H2CO

Homogentisic acidpolyphenol oxidase

Nitisinone

Maleylacetoacetic acid

Citric acid cycle

Alkaptonuria

Formation ofmelanin-like pigment

Oxidation andpolymerization

Benzoquinoneacetic acid

Additional tissue damage

Binding toconnectivetissue

Ascorbic acid

Homogentisate1,2-dioxygenase

4-Hydroxyphenylpyruvicacid dioxygenase

Tyrosine amino transferase

Tyrosine

4-Hydroxyphenylpyruvic acid

Homogentisic acid

Lysyl hydroxylase inhibition

Decreased collagen formation

Free radicalformation

BIOCHEMICAL PATHWAYS LEADING TO OCHRONOSIS

FIG. 212.1 Ochronosis. Pathways leading to pathologic manifestations of ochronosis (alkaptonuria). (Adapted from references 3,9,19.)

FIG. 212.2 Ochronosis. Black-gray pigmentation of the ear cartilage in a patient with ochronosis.

a b

FIG. 212.3 Ochronosis. Radiographs of the spine showing narrowing and calcification of the intervertebral disks.

SECTION 19 Other Arthopathies and Miscellaneous Disorders1770

The extent of arthropathy is typically documented radiographically, and profound osteoarthritic changes are characteristically observed in the large joints and the spine with extensive calcification of intervertebral disks. Magnetic resonance imaging can readily detect ligamentous lesions.27 Bone turnover and bone mass can be determined by quantification of N-telopeptides of type I collagen in the urine and by dual energy x-ray absorptiometry (DXA) of the femur but not by DXA of the spine, for which bone mineral density measurements are spuriously overestimated because of intervertebral disk calcification and osteophyte formation.22 Serum biomarkers shown to be elevated and strongly diagnostic of alkaptonuria comparing patients with healthy control participants included metalloprotease (MMP)-mediated degradation of Titin (TIM) and mimecan (MIM) reflecting cardiovascular remodeling, MMP-mediated collagen type VI (C6M) degradation reflecting cartilage remodeling, and collagen type I degradation (CTX-I) reflecting bone resorption.26 Notably, whereas MMP-mediated collagen type II degradation was the only biomarker reduced in alkaptonuria compared with control participants, it is usually elevated in OA; this was attributed to the extensive pigmentation of cartilage that could make it resistant to remodeling and proteolysis. This supposition is supported by direct analyses of cartilage revealing a very low turnover state and low levels of extractable matrix proteins in alkaptonuria.28 Further studies are required to determine if these biomarkers will facilitate monitoring of treatment responses.

InvasiveMacroscopic inspection of the joint during surgery shows darkened cartilage. Biopsy of affected tissues reveals the characteristic yellow-brown pigment in unstained sections, both free and intracellularly; the pigment typically is seen in macrophages but has also been found in chondrocytes, osteocytes, osteoblasts, osteoclasts, and fibroblasts.29,30 The ochronotic pigmentation is most severe in the deep layer of cartilage, known to be a region of low protein turnover, but the articular surface, the region with the highest level of protein turnover, shows little pigmentation (Fig. 212.5, a).31 Ochronotic fragments of cartilage are found embedded in synovium, where they evoke foreign body reactions with multinucleated giant cells.32 Ochronotic fragments of cartilage are also found in the joint cavity, where they form a nidus for the development of osteochondral bodies.12 Although the molecular basis for this is unclear, by electron microscopy, ochronotic pigment has been observed deposited on collagen fibrils of joint capsule and cartilage, often in a distinctive pattern with some association with the periodicity of collagen cross banding (Fig. 212.5, b)30,33 as well as pigment invasion and disordering of collagen structure.34 This distinct pattern of ochronotic pigment deposition can be reproduced by 5 to 7 days of in vitro culture of osteosarcoma cell lines and chondrocytes in a culture medium supplemented with homogentisic acid.29,35 Interestingly, bone collagen is largely unaffected, which indicates that mineralization of the collagen fibers in vivo prevents deposition of ochronotic pigment.36 Homogentisic acid, the toxic agent in alkaptonuria, was recently identified as a member of a new chemical group of fibroblast growth inhibitors,37 which suggests that the pigment itself may have some antianabolic characteristics that would inhibit the ability of joint tissue to respond to the pathologic insult induced by the deposition of pigment. The antianabolic characteristics of the pigment may, at least in part, explain the general lack of osteophyte formation as described earlier. It has recently been demonstrated that ochronotic pigment co-localizes with amyloid in osteoarticular tissues and is associated with high plasma levels of serum amyloid A and P proteins.38 This suggests that secondary amyloidosis occurs in response to the inflammation invoked by ochronotic pigment. In one report, an aspirate from an affected joint yielded a synovial fluid with a speckled “ground pepper” appearance and dark cytoplasmic inclusions in mononuclear and polymorphonuclear cells.12 Unlike urine, synovial fluids reportedly have low concentrations of homogentisic acid and fail to darken upon addition of alkali.12 Homogentisic acid and its oxidation byproduct, benzoquinone acetic acid, react positively with Nile blue sulfate variant I stain, originally developed for identification of melanin,39 and turn black when stained with methylene blue or cresyl violet.19

DIFFERENTIAL DIAGNOSISAlkaptonuria may be confused with several other conditions that cause dark urine, including porphyrias, the ingestion of indole compounds, myoglobinuria, hemoglobinuria, hematuria, bilirubinuria, and the presence of urobilinogen when oxidized to urobilin.19 The endogenous form of ochronosis may also be confused with exogenous ochronosis. Exogenous ochronosis refers to ochrelike pigment deposition in the skin and sometimes in cartilages or other organs as a result of exposure to a variety of exogenous compounds. Compounds implicated as causative agents of exogenous ochronosis include topical phenol formerly used as an antiseptic, topical hydroquinone bleaching

calcification and stenosis, and coronary artery calcification.9 Because intense pigment deposition is found in the aortic root and minimal pigmentation is seen in the venous circulation, a role has been posited for blood pressure and hemodynamic factors in explaining the differential tissue susceptibility to ochronotic pigmentation and pathologic changes.23

PATHOLOGY INVESTIGATIONSNoninvasiveThe diagnosis of alkaptonuria or ochronosis is suspected when there is bluish black pigmentation of the sclerae and the cartilages of the ears and nose and darkening of the urine on standing in air or with the addition of alkali: 10 drops of 10% NaOH to 20 mL urine (see Zhao24). The diagnosis is confirmed by 24-hour urinary excretion of homogentisic acid, measured by gas chro-matography or high-performance liquid chromatography, that is higher than 0.030 to 0.040 mmol/mmol creatinine for children aged 1 to 6 years and 0.017 mmol/mmol creatinine for individuals from age 7 years through adult-hood.25 In addition, significant laboratory artifacts in alkaptonuria include a false-positive urine Clinitest result for sugars caused by the reduction of copper by homogentisic acid19 and a falsely low urinary creatinine level if measured by an enzymatic method due to interference by homogentisic acid.26

FIG. 212.4 Ochronotic arthritis of the shoulder. Radiograph demonstrating characteristic osteoarthritis pathologic features, including narrowing of the joint space, marked subchondral sclerosis, and small osteophytes.

Characteristics of ochronotic arthropathy versus primary osteoarthritis and ankylosing spondylitis

OchronosisOsteoarthritis (primary)

Ankylosing spondylitis

Joints involved Spine +++ Spine +++ Spine +++Knees +++ Knees ++ Knees +Hips ++ Hips ++ Hips +Shoulders + Hands +++Distinguishing spine features

Sacroiliac joints Spared Spared InvolvedOsteophytosis Sparse Prominent NoneDisk calcification Dense or

waferlikeMild to moderate Mild to moderate

Multiple vacuum disks Common Rare RareSyndesmophytes Broad None Thin + verticalApophyseal facet joint

diseaseMild Mild to severe Severe

Ligamentous ossification

Prominent Scarce Scarce

Adapted from Konttinen YT, Hoikka V, Landtman M, et al. Ochronosis: a report of a case and a review of literature. Clin Exp Rheumatol 1989;7:435-44.

Table 212.1


and brittle, and they fissure and fragment readily. In addition, benzoquinone acetic acid may inhibit lysyl hydroxylase,2 thereby reducing cross-linking of types I and II collagen, further impairing the ability of menisci and articular cartilage to resist stress and shearing injury. Finally, homogentisic acid also inhibits cell growth in vitro in a dose-dependent manner.2 The concentrations of homogentisic acid (1–5 µg/mL) that proved to be cytotoxic in one in vitro study43 corresponded to plasma concentrations reported for patients with alkaptonuria (3.0–27.8 µg/mL).3 Injected in high concentrations into joints of rabbits, homogentisic acid caused swelling, limitation of motion, and articular cartilage necrosis.44

GENETICSIn 1901, Garrod suggested an inherited cause of alkaptonuria6 based on observation of a family with two affected siblings and consanguinity of the parents. In 2007, clinical images of the eye, ear, and spine were published, showing the progression to ochronosis by age 60 years of the infant with alkaptonuria originally identified by Garrod.6 It is now well established that the accumulation of homogentisic acid and its oxidation products occurs through a deficiency of the HGD enzyme. The HGD enzyme is a hexamer consisting of two trimeric subunits.2 The proper folding or association of the HGD subunits can be readily abolished by nonsynonymous (affecting a change in an amino acid) point mutations in the HGD gene on chromosome arm 3q, which eliminates the function of the HGD enzyme at the sites of

creams, quinine injections, oral antimalarial drugs, amiodarone, cytotoxic drugs, minocycline40 (Fig. 212.6), and levodopa and methyldopa used in the treatment of Parkinson disease.41 In most cases, long-term exposure to the inciting agent is necessary for the development of hyperpigmentation. Reversal is slow or nonexistent. These cases are distinguished from endogenous ochronosis by lack of urinary homogentisic acid excretion; genetics; and, in some cases, biopsy findings. No clear clinical effects beyond the cosmetic ones have been delineated for exogenous ochronosis. Thus, it is necessary to appropriately distinguish exogenous from endogenous ochronosis, both to determine prognosis, which is more favorable for exogenous ochronosis, and to recommend the appropriate therapy: withdrawal of the offending agent in the case of exogenous ochronosis; or institution of specific therapies, as described later, for endogenous ochronosis.

PATHOGENESISThe tissue accumulation of homogentisic acid and its oxidation byproduct, benzoquinone acetic acid, is believed to be responsible for the clinical manifestations and severe arthropathy of ochronosis.42 Homogentisic acid can undergo both autoxidation and enzymatic oxidation and polymerization to form an ochronotic pigment in the presence of the enzyme homogentisic acid polyphenol oxidase, present in skin and cartilage42 (see Fig. 212.1). High levels of homogentisic acid perturb collagen assembly and structure in vivo and in vitro.33,34 The infiltrated cartilaginous tissues become stiff31

a b

FIG. 212.5 Ochronosis. (a) Photomicrograph showing the presence of ochronotic pigment in the cartilage from a femoral condyle of a patient with alkaptonuria. Pigmentation appears as a gradient and is most severe in the deep layers of cartilage; the articular surface shows little pigmentation (hematoxylin and eosin [H&E] stain, ×4). Inset: Chondrocytes located on the border between dense and light extracellular pigment. Chondrocytes show intracellular pigmentation and, in some instances, signs of necrosis (H&E stain, ×10). The evidence suggests that pigmentation occurs initially at the deep layers of cartilage before progressing toward the articular surface. (b) Transmission electron micrograph showing collagen fibers of ligamentous capsule from a patient with alkaptonuria. Collagen fibers have numerous electron-dense deposits of ochronotic pigment located along the fiber body. Deposits show some association with collagen cross-banding. Not all fibers have deposits (stained using 1% aqueous osmium tetroxide solution and 5% alcoholic uranyl acetate; poststained using lead citrate and uranyl acetate, ×60,000). (Courtesy of Dr. Adam M. Taylor, findAKUre project, University of Liverpool.)

a b c d

FIG. 212.6 Exogenous ochronosis in a patient treated for more than 10 years with minocycline. Widespread pseudo-ochronosis with black and blue-gray pigmented areas of the skin on the face (a), leg (b), plantar surface of foot (c), and dorsal surface of foot (d). (Courtesy of Dr. Virginia Byers Kraus.)


and reduce the large direct patient health care costs (estimated to be as high as £100,000 depending on disease stage and needs for surgery and patient care).59 A completed prospective randomized clinical trial of nitisinone (2 mg/day for 3 years) in humans (40 patients) reduced plasma and urine homogen-tisic acid by at least 95%; there were few adverse effects (one case each of corneal keratopathy and hepatotoxicity); however, the trial failed to dem-onstrate a conclusive difference in the primary endpoint of hip rotation.55 Nevertheless, among patients lacking aortic stenosis at baseline, none of the 18 nitisinone-treated patients compared with 7 of 17 control patients developed aortic sclerosis by the end of the study.55

An international, multicenter, randomized open-label dose-finding trial called Suitability of Nitisinone in Alkaptonuria 1 (SONIA 1) demonstrated that a 4-week treatment with nitisinone (1-8 mg/day) decreased urinary homogentisic acid to low levels in a dose-dependent manner60 and below the threshold (


Evidence for hyposelenosis in non-KBD areas suggests that other risk factors, in addition to selenium deficiency, contribute to the pathogenesis of KBD. For instance, hyposelenosis exists in non-KBD areas such as Scan-dinavia,91 Poland,92 Central Africa, and the Democratic Republic of the Congo,78,93 although the degree of deficiency in these areas may not be as profound as in the KBD endemic areas.93 Nevertheless, recent data suggest that milder degrees of selenium deficiency are associated with deleterious musculoskeletal consequences. In a population-based study in Johnston County, North Carolina, low selenium levels have been associated with increased odds of knee and hip OA.94 In addition, selenium levels were found to be significantly lower in men than in women in this American cohort.94 As for many essential nutrients, the RDA for selenium is higher for men than for women to compensate for their larger body mass. Thus, it is possible that selenium levels in men may more readily fall below a critical level necessary for joint tissue health under conditions of severely limited intake, suggesting a possible rationale for the consistent reports of a higher prevalence of KBD in men.

CLINICAL FEATURESKashin-Beck disease usually becomes evident in children between 5 and 15 years of age.83 Joint pain is the earliest symptom. For purposes of epidemiologic studies, a diagnosis of KBD has required symptom onset before the age of 30 years to clearly differentiate it from primary OA.95 An increasing number of joints are involved from childhood to the age of 25 years in a slowly progressive osteoarthropathy.96 The particular manifestations of the arthropathy are symmetric and may vary with the time in life of exposure to the endemic environment. In this regard, it is interesting to note an observation attributed to Kravencho in 1959 that an inordinate degree of OA developed in individuals who moved into endemic areas of KBD after the age of 25 years.97 The arthropathy progresses to severe joint dysfunction, enlargement, and deformity. The Chinese characters for this disease, when literally translated, mean “big joint disease”70 (Fig. 212.7). The most distal joints of the lower and upper limbs (lower more than upper) are most often and most severely affected,98,99 including the ankles, knees, interphalangeal joints, wrists, and elbows.95 The foot and ankle are involved in 90% of cases. In fact, it is said that the absence of talus involvement in an adult is cause to reject the diagnosis of KBD.96 The hand develops enlargement of interphalangeal joints reminiscent of Heberden and Bouchard nodes; however, the middle and distal phalanges are shortened, termed brachydactyly (Fig. 212.8 shows a photograph and a radiograph of a hand with KBD), resembling the foreshortened distal and middle phalanges caused by frostbite injury in children.100 The carpal bones, in particular the capitate and hamate, are more likely to be involved with worsening severity of KBD involvement of the hand.101 Short stature is one of the main features of the disease, and dwarfism is sometimes marked, involving a disproportionate shortening of the extremities.97

Standardized national clinical and radiologic diagnostic criteria for KBD have been available in China since 1995 (clinical GB16003-1995) (Table 212.2) and 2001 (radiologic W/T 207-2001) (Table 212.3); their correlation with other features of KBD, including brachydactyly, has been evaluated.102 In addition, other staging systems have been devised for this disorder based on clinical70,95,103 or radiologic96,98,101 features (see Tables 212.1 and 212.2). A significant correlation has been shown between the clinical classification system of Mathieu95 and the radiologic classification system of Hinsenkamp.98

stress.75 These endemic regions are known for especially low environmental levels of the essential trace element selenium76 and, consequently, low selenium levels in the blood and tissues of the native peoples consuming food from these areas.77 The population mean serum selenium concentration in this region is less than 0.020 mg/L,78 but serum selenium concentrations in healthy persons have been found to average 0.066 to 0.104 mg/L.79 In China, the geographic distribution of KBD corresponds most closely to the areas of lowest selenium in water, soil, and food grains,76,80 and fluctuations in disease status are reported to correspond to fluctuations in serum selenium concentra-tion,76 the so-called wave character in morbidity.68 The daily intake of selenium in the Shaanxi KBD endemic area of China was quantified as 4.6 µg/day compared with 10.5 µg/day for nonendemic areas.81 Both levels are well below the U.S. recommended daily allowance (RDA) of 70 µg for men and 55 µg for women. Within low-selenium areas, the reliance on river water for drinking has been associated with increased risk of disease in KBD areas, although selenium levels of the various water sources under study were not cited.82 Whereas eating corn, wheat, and barley has also been associated with KBD, eating rice appears to be protective74,76; interestingly, rice grown in KBD-endemic areas has a higher selenium content and selenium bioavail-ability than corn or wheat, which possibly accounts for its apparently protective effect.

Although a geographic association between KBD and selenium deficiency has been reported, KBD does not occur in every selenium-deficient area of China.78 Therefore, to gain a comprehensive understanding of risk factors for KBD, a cross-sectional epidemiologic study was conducted in 12 rural villages in Tibet in which 575 children aged 5 to 15 years were examined. The variables independently associated with KBD were found to be higher age, male gender, low socioeconomic status, a poorly diversified diet, iodine deficiency, and the use of smaller water containers.74 Individuals were also at greatest risk of KBD if they had a sibling with the disease. In this study, whereas selenium deficiency was severe in both KBD-affected and unaffected children, low urinary iodine, high serum thyrotropin, and low serum thyroxine-binding globulin values were associated with an increased risk of KBD. Goiter secondary to iodine deficiency was found more often in villages affected by KBD than in control villages.83 In general, selenium deficiency is closely associated with iodine deficiency in KBD areas.78,83 In one KBD-endemic area of China, urinary iodine levels were found to be 40% lower in KBD-affected children than in unaffected children.84 Although iodine deficiency doubled the odds of KBD in this Chinese cohort, selenium deficiency was associated with a 61-fold increase in the odds of KBD.

In China, foodstuffs such as corn were commonly stored in cave dwellings, where it is believed mycotoxins entered the food chain. In Tibet, too, a striking association was found between KBD and moldy grain from storage in a tent out of doors, which further suggests a pathogenic role for myco-toxins.74 Fungal contamination of barley grain was related to the highest percentage of KBD cases (65%). Three fungal taxa isolated from barley samples were independently associated with KBD (Trichothecium roseum, Alternaria spp., and Dreschlera spp.). The KBD prevalence rate increased dramatically from 13% if none of these taxa was isolated to 51% if one taxon was found and 89% if two or more taxa were isolated. This study provided strong support for a multifactorial cause of KBD in Tibet. Since then, numerous in vitro and animal studies have documented the deleterious effect of mycotoxins on cartilage.85-90 The consequences of selenium deficiency may be exacerbated by the oxidative stress resulting from the fungal exposures.

a b

FIG. 212.7 Kashin-Beck disease manifested as bony enlargement of the elbows (a) and knees (b), exemplifying the characteristic for which the disease is named big joint disease in China. (Courtesy of Drs. Virginia Byers Kraus and Junling Cao.)


urine OA-related biomarkers have been shown to be associated with the presence or severity of KBD, including chondroitin sulfate and proteoglycan-related epitopes, pyridinoline, serum nitric oxide, CD44, MMP-1, interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), cartilage oligomeric matrix protein, and C-telopeptide of type II collagen (CTXII).106-111 Proteomic studies comparing KBD and control sera are ongoing to identify diagnostic biomarkers for KBD.112,113

InvasiveThe initial pathologic change in KBD is necrosis of cartilage and secondary repair and remodeling of cartilages of the metaphyses, bone ends, epiphyses, and carpal bones,96 leading to disturbed mineralization, impaired skeletal development, disfiguration of joints, and chronic deforming OA.103,114 Because the metaphyseal side of the growth plate is the most active site of bone growth and development during childhood, it is the site affected earliest and most frequently with cartilage necrosis (termed chondronecrosis).96 Apoptotic chondrocytes are found more frequently in KBD than in control cartilage115

Although the clinical criteria are more sensitive, the radiologic criteria are more specific for KBD.98 An instrument for assessing quality of life has recently been developed and validated for use in KBD patient populations.104

PATHOLOGY INVESTIGATIONSNoninvasiveThe abnormalities of growth and development and the radiographic appearance of this disease have been ascribed to pathologic endochondral growth at epiphyseal and acrophyseal sites.105 The radiologic features of KBD have been reported to resemble the lesions of osteochondrosis,70 a group of diseases of children and adolescents that are caused by insufficient blood supply to the epiphyses that leads to localized tissue necrosis at the growing ends of bones during the years of rapid bone growth. The radiologic joint features deemed diagnostic of KBD include irregularities of bony margins; sclerosis; and a cone-shaped, fused, or fragmented metaphysis.92 Several serum and

a b

FIG. 212.8 Kashin-Beck disease (KBD) of the hand. (a) Photograph of a hand with the brachydactyly of KBD (left) compared with a reference hand of a Chinese individual without KBD (right). (b) Radiograph of the hand of an individual with KBD demonstrating shortened middle and distal phalanges, cone-shaped metaphyses, and “pumice stone” deformity of the carpal bones. (a, Courtesy of Dr. Junling Cao; b, courtesy of Dr. Xiong Guo.)

Staging systems for Kashin-Beck diseaseClinical staging system based on the Chinese National Criteria

Stage SignsEarly Flexion of the terminal part of the fingers or crooked fingers and arthritis pain in knee and ankle joints without enlarged finger jointsFirst stage Enlarged finger joints and clinical symptoms of the early stageSecond stage Shortened fingers and clinical symptoms of the first stageThird stage Retarded growth or dwarfism and clinical symptoms of the second stage

Clinical staging system of Mathieu

Stage AgeJoint enlargement (caused by metaphyseal widening) Joint pain

Severity of motion restriction of most affected joint Associated symptoms*

I


concentrations have been documented in endemic KBD areas of China;123 this has many adverse biological effects. For instance, suppression of the selenoprotein iodothyronine deiodinase-2 (DIO2, responsible for conversion of thyroid hormone to its active form) results in strong proinflammatory effects with increased expression of inflammatory mediators, IL-1β, and cyclooxygenase-2 (COX-2).124 In addition, low selenium results in inadequate antioxidant defense caused by a lack of selenoprotein antioxidants such as glutathione peroxidase and thioredoxin reductase. It is posited that free radicals, generated by mycotoxins and fulvic acid or other environmental factors, damage chondrocytes under conditions of inadequate antioxidant defense, iodine deficiency, and possible protein-calorie malnutrition.74 This is supported by results showing that selenium can partially counteract adverse chondral effects of the fungal toxin T-2125 and IL-1.126 Taken together, these results underscore the key chondroprotective and antiinflammatory role performed by selenium. In the absence of adequate selenium and antioxidant defense, the final common pathway of pathogenesis is chondrocyte apoptosis127 and necrosis of the hypertrophic chondrocytes at the base of the articular and growth plate cartilages.128

Selenium is necessary for the growth of cells in tissue culture91 and is commonly used (in the form of selenite) as a supplement for chondrocyte culture in combination with insulin and transferrin.129 Selenium bioavailability ultimately depends on both intestinal absorption of selenium and its conversion into a biochemically active form.130 Selenomethionine, the major form of selenium found in food, has almost twice the bioavailability of selenium in the form of selenite.131 Brief (24-hour) exposure of chondrocytes in vitro to selenomethionine (0.5–1.0 µmol/L) has been shown to block IL-1–mediated inhibition of cartilage matrix macromolecule (collagen II, aggrecan) synthesis, transforming growth factor-β2 receptor synthesis,132 and inducible nitric oxide synthase and COX-2 expression responsible for nitric oxide and prostaglandin E2 production, respectively.

126

Some chondrotoxic effects and other pathologic effects have been attributed to mycotoxins and fulvic acid. Nivalenol, a mycotoxin produced by Fusarium spp., inhibits protein synthesis by binding to the ribosome. Added to cartilage grafts in vitro, nivalenol inhibits glycosaminoglycan synthesis and retention in the extracellular matrix, overall reducing the chondroitin sulfate content of cartilage.133,134 It has been hypothesized that mycotoxins may inhibit angiogenesis,98 block thyroid hormone function,74 and bind thyroid receptors in bone cells.74 When added to the diet of rats, fungal extracts inhibit glu-tathione peroxidase and superoxide dismutase activities and accelerate lipid peroxidation.135 Similarly, it is hypothesized that organic matter in the form of fulvic acid may accumulate in musculoskeletal tissues and induce superoxide production via its semiquinone radicals136 and lipid peroxidation.135 These, in turn, would be poorly scavenged in a selenium-deficient host with low levels of glutathione peroxidase activity. In vitro, fulvic acid stimulates the generation of H2O2 by chondrocytes and increases collagen secretion in a H2O2-dependent manner.

137 Fulvic acid has also been shown to inhibit the conversion of procollagen II to mature collagen II.71 However, the levels used in these experiments have not been equated to blood or tissue levels of affected individuals in endemic areas. Finally, this family of organic acids may interfere with selenium absorption from the intestine.138

GENETICSAs described earlier, hyposelenosis may be necessary but not sufficient to cause disease. Within the low-selenium belt in China, there are some places and individuals without KBD even though selenium concentrations in the soil, food grains, and hair are low.139,140 The mosaic character of disease prevalence (affected villages next to healthy ones) was noted as early as 1939.68 In his extensive review of the KBD literature from 1849 to 1992,70 ALLANDER noted instances of Chinese villages where KBD was endemic within 30 to 50 miles of villages where KBD was nonexistent. This suggests that other environmental or as yet unknown genetic factors are required for full manifestation of the syndrome. Clustering within families has been noted.74,128 Genetic factors, common environmental risk factors, or a combina-tion of both could account for this clustering. A 2006 to 2007 survey of 212 case and 212 control families (total of 3848 individuals) reported that use of river water as the main source of drinking water clustered in KBD families and accounted for a sixfold increase in the odds of KBD.82 The proportion of KBD-affected relatives among the probands’ families was substantial and significantly higher than that in the control families (55.4% vs 10.2%, respectively; P = 0.0001).82 Neither drinking river water alone nor other dietary factors fully explained the familial aggregation of KBD. In a companion study, the heritability of KBD was estimated to be 29% in Linyou County, China.141 These observations suggest that other factors influence the develop-ment of disease. Nevertheless, until recently, the possibility of a genetic component of disease susceptibility has generally been overlooked in favor

and at a rate comparable to that in OA. The histologic features of KBD lesions have included the absence of vascularization within the proximal cartilage endplate.116 In vitro studies of cartilage or chondrocytes have demonstrated increased hydroxyproline content, decreased thermal stability of collagen II, and increased levels of precursor collagen (procollagen II) thought possibly caused by inhibition of conversion to the mature collagen II,71 as well as decreased collagen II; increased collagens I, III, and X; increased MMP-13117,118; and increased aggrecanase-generated proteoglycan loss from cartilage.108 These effects were ascribed to fulvic acid toxicity and possibly other environmental exposures.

DIFFERENTIAL DIAGNOSISSelenium and iodine deficiency are linked geographically. Distinguishing between the radiologic features of hypothyroidism and KBD can be difficult, requiring expert radiographic opinion.78 It has been thought possible that some of the musculoskeletal abnormalities of KBD may be related to thyroid dysfunction early in life83 because hypothyroidism in children is associated with epiphyseal dysgenesis, delay of bone development, and reduced endo-chondral ossification. Of note, selenium plays an indispensable role in thyroid hormone synthesis because it is required for iodothyronine deiodinase activity that coverts thyroxine (T4) to the more active triiodothyronine (T3).

92 Thus, a closer examination of the role of thyroid hormone abnormalities in the pathogenesis of KBD appears to be warranted.

PATHOGENESISTo date, no consensus has been reached on the cause of KBD. Early residents of the Urov River Valley associated it with “bad” drinking water and had a notion that the disease could be passed down from generation to generation in “diseased families.”68 Three causal mechanisms have been proposed to interact to cause KBD:■ A deficiency in trace elements (selenium and iodine)119

■ The presence of organic matter in drinking water (fulvic and humic acid produced by chemical and microbial decomposition of plants and animals)76,82

■ Contamination of food by noxious mycotoxins, bacterial toxins, or both120-122

Cold exposure and occupational microtrauma have also been implicated in disease severity.99 In this model, a low selenium level is an essential but insufficient condition for the development of KBD.76 Low selenium blood

Radiologic staging systems for Kashin-Beck disease

Radiologic staging system based on the Chinese National CriteriaGrade Basis for grade (features scored below)Normal 0 pointsMild 1–4 pointsModerate 5–7 pointsSevere 8–10 points

Possible points Radiologic features3 Osteophyte: absent = 0;


prevent its occurrence. The strategy of selenium supplementation is considered the mainstay of therapy for KBD in China. Daily intakes of selenium below 20 µg are considered insufficient.161 The U.S. RDA is based on optimization of plasma glutathione peroxidase concentrations; however, the amount of selenium needed to optimize selenoprotein P levels may be greater than the current U.S. RDA.131 The plasma selenium concentration is often used to assess selenium nutritional status. At plasma concentrations of about 0.08 mg/L (0.4 µmol/L), the selenoproteins glutathione peroxidase and selenoprotein P are considered optimized.131 Selenium supplementation in China has been effected through the distribution of selenium-enriched table salt, the distribu-tion of selenium tablets to children,80 and the use of selenium-enriched fertilizer.70,81 A meta-analysis of 11 community based trials involving 2652 children (1677 children treated with salt enriched with selenium at a ratio of 1 : 60,000 for most of the studies and 975 control children treated with edible salt) showed that selenium-enriched salt prevented KBD in healthy children (odds ratio [OR], 0.16), improved clinical symptoms in children with KBD (OR, 6.57), and led to repair of metaphyseal lesions based on radiographic evidence (OR, 5.53) but not repair of the distal ends of phalangeal lesions.162 The use of selenium-enriched fertilizer in selenium-deficient areas has been shown to increase the average daily intake of selenium as much as fourfold to 16.8 µg/day.81 Excess selenium is toxic, so dosages must be carefully regulated; side effects of excess selenium include adverse effects on the mechanical properties of bones,114 hair and nail loss,163 neurologic dysfunction and respiratory distress,164 and death.79 The toxicity limit is estimated to be 600 to 800 µg/day.161,163 However, the 1 : 60,000 ratio of salt to selenium is considered to be nontoxic and without side effects with long-term use.162

In KBD-affected areas of Tibet, where both selenium and iodine deficiency are endemic, supplementation of iodine over 12 months was primarily responsible for stimulating the growth of a population of 10-year-old chil-dren.119 As described earlier, a 12-month study of Tibetan children showed the beneficial effects of repleting iodine in cases of KBD associated with both iodine and selenium deficiency. Because selenium repletion may aggravate hypothyroidism,119 iodine must be administered before selenium in cases in which both are deficient.119 This study has suggested the importance of iodine deficiency as an etiologic factor for KBD manifestations in some areas. Although not significant, new radiologic lesions occurred only in the group given iodine only (3 of 71 children) and not in the group given both selenium and iodine (0 of 90 children), which suggests a potential role for selenium therapy as well.

Other preventive efforts include providing better storage of crops, drying corn, shifting to other crops less susceptible to fungal contamination and with greater bioavailability of selenium (e.g., from corn to rice),70,98 and improving the quality of drinking water.71 Standard treatments for OA, including physical therapy, nonsteroidal antiinflammatory agents, nutraceu-ticals, and intraarticular hyaluronan, may also be of benefit in cases of established KBD.165-168 Some individuals undergo osteotomy169 or extraction of loose bodies and joint lavage by arthroscopy,170 but currently joint replace-ment is uncommon because of cost barriers.

ACKNOWLEDGEMENTSThe author wishes to thank Dr. Christopher McCudden for his invaluable assistance with graphics. She also wishes to thank Dr. Adam Taylor for providing photographs illustrative of ochronosis and Drs. Bruce Caterson, Junling Cao, and Xiong Guo for providing photographs illustrative of KBD.

of environmental risk factors. To date, reported genetic variants associated with KBD have included those shown in Box 212.1.

ANIMAL MODELSMice fed for two generations on a selenium-deficient diet supplemented with fulvic acid in the drinking water demonstrated disturbed development of the articular space and meniscus, disturbed subchondral ossification, overly hydroxylated collagens I and II with less thermal stability, and low bone formation activity.136,153 Second-generation rats fed a selenium-deficient diet showed growth retardation, a reduction in pituitary growth hormone and plasma insulin-like growth factor I levels, and impaired bone metabolism and osteopenia.154 Chronic selenium deficiency in rats was also associated with abnormalities of chondrocytes in the deep cartilage layers consisting of nuclear degeneration and ballooning of the endoplasmic reticulum.155 Combined selenium and iodine deficiency in rats significantly impaired the growth of bone and cartilage.156 Rats developed chondronecrosis and features of KBD when fed a selenium-deficient diet followed by oral challenges with A-1 toxin (bacterial contaminant of grain)157 or T-2 mycotoxin (fungal contaminant of grain).158 Conversely, mice prone to OA (the STR/1N strain) were protected from disease while on a diet enriched with vitamins (C, E, A, and B6) and selenium.

159 The role played by muscle in this disease has also been questioned. Severe white muscle lesions develop in sheep in response to low selenium levels. Therefore, the possibility has been raised that muscle weakness may contribute directly to the musculoskeletal abnormalities of KBD.70

Strong support for a definitive role of selenium deficiency in KBD has recently been provided by a mouse model in which the gene encoding the selenocysteine transfer RNA, essential for selenoprotein expression, has been deleted from chondrocytes.160 The mice manifested a number of pathologic features typical of KBD (chondronecrosis of articular cartilage, ear cartilage, and tracheal cartilage; small spine size; disproportionate widening of the epiphyseal growth plates) and died by 7 weeks of age due to respiratory distress from tracheomalacia.

MANAGEMENTIndividuals with radiologic lesions have more advanced stages of the disease and are expected to be less influenced by selenium treatment than individuals without radiologic lesions.119 Therefore, the key to managing KBD is to

BOX 212.1 GENETIC VARIANTS ASSOCIATED WITH KBD

HLA-DRB1142,143

Tumor necrosis factor-α144

CD-2–associated protein (CD2AP)143

ABI gene family member 3-binding protein (ABI3BP)145

Glutathione peroxidase 1 (GPX1)146

Glutathione peroxidase 4 (GPX4)147

Growth differentiation factor 5 (GDF5)148,149

DIO2148

Peroxisome proliferator-activated receptor γ coactivator 1-β (PPARGC1B)150

Fibroblast growth factor 12 (FGF12)151

Disintegrin and metalloproteinase domain–containing protein 12 (ADAM12)33,152

REFERENCES1. Gallagher JA, Dillon JP, Sireau N, et al. Alkaptonuria: an

example of a “fundamental disease”–a rare disease with important lessons for more common disorders. Semin Cell Dev Biol. 2016;52:53-57.

2. Mannoni A, Selvi E, Lorenzini S, et al. Alkaptonuria, ochronosis, and ochronotic arthropathy. Semin Arthritis Rheum. 2004;33(4):239-248.

3. Phornphutkul C, Introne WJ, Perry MB, et al. Natural history of alkaptonuria. N Engl J Med. 2002;347(26):2111-2121.

4. Rosenberg LE. Legacies of Garrod’s brilliance. One hundred years–and counting. J Inherit Metab Dis. 2008;31(5):574-579.

5. Kobak AC, Oder G, Kobak S, et al. Ochronotic arthropathy: disappearance of alkaptonuria after liver

transplantation for hepatitis B-related cirrhosis. J Clin Rheumatol. 2005;11(6):323-325.

6. Watts RW, Watts RA. Alkaptonuria: a 60-yr follow-up. Rheumatology (Oxford). 2007;46(2):358-359.

7. Stenn FF, Milgram JW, Lee SL, et al. Biochemical identification of homogentisic acid pigment in an ochronotic Egyptian mummy. Science. 1977;197(4303):566-568.

8. Lamy S. Orphan drugs: final study. In: European Parliament. Directorate General for Research; 1999.

9. Keller JM, Macaulay W, Nercessian OA, et al. New developments in ochronosis: review of the literature. Rheumatol Int. 2005;25(2):81-85.

10. Uyguner O, Goicoechea de Jorge E, Cefle A, et al. Molecular analyses of the HGO gene mutations in

Turkish alkaptonuria patients suggest that the R58fs mutation originated from central Asia and was spread throughout Europe and Anatolia by human migrations. J Inherit Metab Dis. 2003;26(1):17-23.

11. Al-Sbou M, Mwafi N, Lubad MA. Identification of forty cases with alkaptonuria in one village in Jordan. Rheumatol Int. 2012;32(12):3737-3740.

12. Hunter T, Gordon DA, Ogryzlo MA. The ground pepper sign of synovial fluid: a new diagnostic feature of ochronosis. J Rheumatol. 1974;1(1):45-53.

13. Peker E, Yonden Z, Sogut S. From darkening urine to early diagnosis of alkaptonuria. Indian J Dermatol Venereol Leprol. 2008;74(6):700.

14. Burkhart C, Burkhart C Ochronosis. In: eMedicine Specialities; 2005.


15. Vijaikumar M, Thappa DM, Srikanth S, et al. Alkaptonuric ochronosis presenting as palmoplantar pigmentation. Clin Exp Dermatol. 2000;25(4):305-307.

16. Hamdi N, Cooke TD, Hassan B. Ochronotic arthropathy: case report and review of the literature. Int Orthop. 1999;23(2):122-125.

17. Perry MB, Suwannarat P, Furst GP, et al. Musculoskeletal findings and disability in alkaptonuria. J Rheumatol. 2006;33(11):2280-2285.

18. Orzincolo C, Castaldi G, Scutellari PN, et al. [Ochronotic arthropathy in alkaptonuria. Radiological manifestations and physiopathological signs]. Radiol Med (Torino). 1988;75(5):476-481.

19. Konttinen YT, Hoikka V, Landtman M, et al. Ochronosis: a report of a case and a review of literature. Clin Exp Rheumatol. 1989;7(4):435-444.

20. Filippou G, Frediani B, Selvi E, et al. Tendon involvement in patients with ochronosis: an ultrasonographic study. Ann Rheum Dis. 2008;67(12):1785-1786.

21. Chua SY, Chang HC. Bilateral spontaneous rupture of the quadriceps tendon as an initial presentation of alkaptonuria–a case report. Knee. 2006;13(5):408-410.

22. Aliberti G, Pulignano I, Schiappoli A, et al. Bone metabolism in ochronotic patients. J Intern Med. 2003;254(3):296-300.

23. Helliwell TR, Gallagher JA, Ranganath L. Alkaptonuria–a review of surgical and autopsy pathology. Histopathology. 2008;53(5):503-512.

24. Zhao BH, Chen BC, Shao DC, et al. Osteoarthritis? Ochronotic arthritis! A case study and review of the literature. Knee Surg Sports Traumatol Arthrosc. 2009;17(7):778-781.

25. Olah AV, Llyes I, Szoke A, et al. Urinary homogentisic acid in alkaptonuric and healthy children. Clin Chem Lab Med. 2003;41(3):356-359.

26. Genovese F, Siebuhr AS, Musa K, et al. Investigating the robustness and diagnostic potential of extracellular matrix remodelling biomarkers in alkaptonuria. JIMD Rep. 2015;24:29-37.

27. Perrone A, Impara L, Bruni A, et al. Radiographic and MRI findings in ochronosis. Radiol Med. 2005;110(4):349-358.

28. Taylor A, Hsueh M-F, Ranganath L, et al. Cartilage biomarkers in the osteoarthropathy of alkaptonuria reveal low turnover and accelerated aging. Rheumatology (Oxford). 2017;56(1):156-164.

29. Taylor A, Fraser W, Wilson P, et al. Ultrastructural analysis of collagen in the arthropathy of alkaptonuria in vivo and in vitro. Osteoarthritis Cartilage. 2009;17(suppl 1):S244-S245.

30. Taylor AM, Wlodarski B, Prior IA, et al. Ultrastructural examination of tissue in a patient with alkaptonuric arthropathy reveals a distinct pattern of binding of ochronotic pigment. Rheumatology (Oxford). 2010;49(7):1412-1414.

31. Taylor AM, Boyde A, Wilson PJ, et al. The role of calcified cartilage and subchondral bone in the initiation and progression of ochronotic arthropathy in alkaptonuria. Arthritis Rheum. 2011;63(12):3887-3896.

32. Kruithof E, Baeten D, Veys EM, et al. Case number 29: Ochronosis: synovial histopathological characteristics. Ann Rheum Dis. 2004;63(2):130.

33. Taylor A, Prio I, Wlodarski B, et al. Ultrastructural examination of collagen from alkaptonuric tissue provides clues to pathogenesis of ochronosis. Calcif Tissue Int. 2008;83:33.

34. Chow WY, Taylor AM, Reid DG, et al. Collagen atomic scale molecular disorder in ochronotic cartilage from an alkaptonuria patient, observed by solid state NMR. J Inherit Metab Dis. 2011;34(6):1137-1140.

35. Tinti L, Taylor AM, Santucci A, et al. Development of an in vitro model to investigate joint ochronosis in alkaptonuria. Rheumatology (Oxford). 2011;50(2):271-277.

36. Taylor A, Fraser W, Wilson P, et al. Ultrastructural studies on the binding of ochronotic pigment to collagen fibres in cartilage and bone in vivo and in vitro. Calcif Tissue Int. 2009;85:187.

37. Fernandez IS, Cuevas P, Angulo J, et al. Gentisic acid, a compound associated with plant defense and a metabolite of aspirin, heads a new class of in vivo fibroblast growth factor inhibitors. J Biol Chem. 2010;285(15):11714-11729.

38. Millucci L, Spreafico A, Tinti L, et al. Alkaptonuria is a novel human secondary amyloidogenic disease. Biochim Biophys Acta. 2012;1822(11):1682-1691.

39. Blivaiss BB, Rosenberg EF, Kutuzov H, et al. Experimental ochronosis. Induction in rats by long-term feeding with L-tyrosine. Arch Pathol. 1966;82(1):45-53.

40. Suwannarat P, Phornphutkul C, Bernardini I, et al. Minocycline-induced hyperpigmentation masquerading as alkaptonuria in individuals with joint pain. Arthritis Rheum. 2004;50(11):3698-3701.

41. Rausing A, Rosen U. Black cartilage after therapy with levodopa and methyldopa. Arch Pathol Lab Med. 1994;118(5):531-535.

42. Hegedus ZL, Nayak U. Homogentisic acid and structurally related compounds as intermediates in plasma soluble melanin formation and in tissue toxicities. Arch Int Physiol Biochim Biophys. 1994;102(3):175-181.

43. Kirkpatrick CJ, Mohr W, Mutschler W. Experimental studies on the pathogenesis of ochronotic arthropathy. The effects of homogentisic acid on adult and fetal articular chondrocyte morphology, proliferative capacity and synthesis of proteoglycans in vitro. Virchows Arch B Cell Pathol Incl Mol Pathol. 1984;47(4):347-360.

44. Moran TJ, Yunis EJ. Studies on ochronosis. 2. Effects of injection of homogentisic acid and ochronotic pigment in experimental animals. Am J Pathol. 1962;40:359-369.

45. Fernandez-Canon JM, Granadino B, Beltran-Valero de Bernabe D, et al. The molecular basis of alkaptonuria. Nat Genet. 1996;14(1):19-24.

46. Laschi M, Tinti L, Braconi D, et al. Homogentisate 1,2 dioxygenase is expressed in human osteoarticular cells: implications in alkaptonuria. J Cell Physiol. 2012;227(9):3254-3257.

47. Zatkova A, Sedlackova T, Radvansky J, et al. Identification of 11 novel homogentisate 1,2 dioxygenase variants in alkaptonuria patients and establishment of a novel LOVD-based HGD mutation database. JIMD Rep. 2012;4:55-65.

48. Zatkova A. An update on molecular genetics of alkaptonuria (AKU). J Inherit Metab Dis. 2011;34(6):1127-1136.

49. Al-sbou M. Novel mutations in the homogentisate 1,2 dioxygenase gene identified in Jordanian patients with alkaptonuria. Rheumatol Int. 2012;32(6):1741-1746.

50. Vilboux T, Kayser M, Introne W, et al. Mutation spectrum of homogentisic acid oxidase (HGD) in alkaptonuria. Hum Mutat. 2009;30(12):1611-1619.

51. Montagutelli X, Lalouette A, Coude M, et al. aku, a mutation of the mouse homologous to human alkaptonuria, maps to chromosome 16. Genomics. 1994;19(1):9-11.

52. Taylor AM, Preston AJ, Paulk NK, et al. Ochronosis in a murine model of alkaptonuria is synonymous to that in the human condition. Osteoarthritis Cartilage. 2012;20(8):880-886.

53. Introne WJ, Kayser MA, Gahl WA. Alkaptonuria. In: Pagon RA, Bird TD, Dolan CR, et al, eds. GeneReviews. Seattle: University of Washington, 1993.

54. Suwannarat P, O’Brien K, Perry MB, et al. Use of nitisinone in patients with alkaptonuria. Metabolism. 2005;54(6):719-728.

55. Introne WJ, Perry MB, Troendle J, et al. A 3-year randomized therapeutic trial of nitisinone in alkaptonuria. Mol Genet Metab. 2011;103(4):307-314.

56. Olsson B, Cox TF, Psarelli EE, et al. Relationship between serum concentrations of nitisinone and its effect on homogentisic acid and tyrosine in patients with alkaptonuria. JIMD Rep. 2015;24:21-27.

57. Preston AJ, Keenan CM, Sutherland H, et al. Ochronotic osteoarthropathy in a mouse model of alkaptonuria, and its inhibition by nitisinone. Ann Rheum Dis. 2014;73(1):284-289.

58. Keenan CM, Preston AJ, Sutherland H, et al. Nitisinone arrests but does not reverse ochronosis in alkaptonuric mice. JIMD Rep. 2015;24:45-50.

59. Simoncelli M, Samson J, Bussières JF, et al. Cost-consequence analysis of nitisinone for treatment of tyrosinemia type I. Can J Hosp Pharm. 2015;68(3):210-217.

60. Ranganath LR, Milan AM, Hughes AT, et al. Suitability of nitisinone in alkaptonuria 1 (SONIA 1): an international, multicentre, randomised, open-label, no-treatment controlled, parallel-group, dose-response

study to investigate the effect of once daily nitisinone on 24-h urinary homogentisic acid excretion in patients with alkaptonuria after 4 weeks of treatment. Ann Rheum Dis. 2016;75(2):362-367.

61. Cox TF, Ranganath L. A quantitative assessment of alkaptonuria: testing the reliability of two disease severity scoring systems. J Inherit Metab Dis. 2011;34(6):1153-1162.

62. Ranganath LR, Cox TF. Natural history of alkaptonuria revisited: analyses based on scoring systems. J Inherit Metab Dis. 2011;34(6):1141-1151.

63. Arnoux JB, Le Quan Sang KH, Brassier A, et al. Old treatments for new insights and strategies: proposed management in adults and children with alkaptonuria. J Inherit Metab Dis. 2015;38(5):791-796.

64. Braconi D, Laschi M, Amato L, et al. Evaluation of anti-oxidant treatments in an in vitro model of alkaptonuric ochronosis. Rheumatology (Oxford). 2010;49(10):1975-1983.

65. Tinti L, Spreafico A, Braconi D, et al. Evaluation of antioxidant drugs for the treatment of ochronotic alkaptonuria in an in vitro human cell model. J Cell Physiol. 2010;225(1):84-91.

66. Braconi D, Bernardini G, Paffetti A, et al. Comparative proteomics in alkaptonuria provides insights into inflammation and oxidative stress. Int J Biochem Cell Biol. 2016;81(Pt B):271-280.

67. Englard S, Seifter S. The biochemical functions of ascorbic acid. Ann Rev Nutr. 1986;6:365-406.

68. Voshchenko A. Kashin-Beck disease in USSR. In: Proceedings of the International Workshop on Kashin-Beck Disease and Non-communicable Diseases. Beijing: World Health Organization; 1990:152-196.

69. Jianbo Y. Epidemiological studies on the causes of Kashin-Beck disease. In: Proceedings of the International Workshop on Kashin-Beck Disease and Non-communicable Diseases. Beijing: World Health Organization; 1990:63-78.

70. Allander E. Kashin-Beck disease. An analysis of research and public health activities based on a bibliography 1849-1992. Scand J Rheumatol Suppl. 1994;99:1-36.

71. Yang CL, Bodo M, Notbohm H, et al. Fulvic acid disturbs processing of procollagen II in articular cartilage of embryonic chicken and may also cause Kashin-Beck disease. Eur J Biochem. 1991;202(3):1141-1146.

72. Fu Q, Cao J, Caterson B, et al. Radiographic features of hand osteoarthritis in adult Kashin-Beck disease (KBD): the Yongshou KBD Study. Osteo Cartilage. 2015;23(6):868-873.

73. Zou K, Liu G, Wu T, et al. Selenium for preventing Kashin-Beck osteoarthropathy in children: a meta-analysis. Osteoarthritis Cartilage. 2009;17(2):144-151.

74. Suetens C, Moreno-Reyes R, Chasseur C, et al. Epidemiological support for a multifactorial aetiology of Kashin-Beck disease in Tibet. Int Orthop. 2001;25(3):180-187.

75. Mathieu F, Begaux F, Suetens C, et al. Anthropometry and clinical features of Kashin-Beck disease in central Tibet. Int Orthop. 2001;25(3):138-141.

76. Jiang Y, Xu G. The relativity between some epidemiological characteristics of Kashin-Beck disease and selenium deficiency. In: Wendel A, ed. Selenium in Biology and Medicine. New York: Springer; 1989: 263-269.

77. Dongxu M. Advances in the pathology of Kashin-Beck disease and its relationship with selenium and other elements. In: Proceedings of the International Workshop on Kashin-Beck Disease and Non-communicable Diseases. Beijing: World Health Organization; 1990:42-55.

78. Moreno-Reyes R, Suetens C, Mathieu F, et al. Kashin-Beck osteoarthropathy in rural Tibet in relation to selenium and iodine status. N Engl J Med. 1998;339(16):1112-1120.

79. Baselt R. Selenium. In: Disposition of Toxic Drugs and Chemicals in Man. 6th ed. Foster City, CA: Biomedical Publications; 2002:955-959.

80. Ge K, Yang G. The epidemiology of selenium deficiency in the etiological study of endemic diseases in China. Am J Clin Nutr. 1993;57(2 suppl):259S-263S.

81. Xu LQ, Sen WX, Xiong QH, et al. Selenium in Kashin-Beck disease areas. Biol Trace Elem Res. 1991;31(1):1-9.


82. Zhang Y, Guo X, Ping Z, et al. Main source of drinking water and familial aggregation of Kashin-Beck disease: a population based on case-control family study. Ann Epidemiol. 2009;19(8):560-566.

83. Moreno-Reyes R, Suetens C, Mathieu F, et al. Kashin-Beck disease and iodine deficiency in Tibet. Int Orthop. 2001;25(3):164-166.

84. Zhang WH, Neve J, Xu JP, et al. Selenium, iodine and fungal contamination in Yulin District (People’s Republic of China) endemic for Kashin-Beck disease. Int Orthop. 2001;188-190.

85. Tian J, Yan J, Wang W, et al. T-2 toxin enhances catabolic activity of hypertrophic chondrocytes through ROS-NF-kappaB-HIF-2alpha pathway. Toxicol In Vitro. 2012;26(7):1106-1113.

86. Lu M, Cao J, Liu F, et al. The effects of mycotoxins and selenium deficiency on tissue-engineered cartilage. Cells Tissues Organs. 2012;196(3):241-250.

87. Chen JH, Xue S, Li S, et al. Oxidant damage in Kashin-Beck disease and a rat Kashin-Beck disease model by employing T-2 toxin treatment under selenium deficient conditions. J Orthop Res. 2012;30(8):1229-1237.

88. Guan F, Li S, Wang ZL, et al. Histopathology of chondronecrosis development in knee articular cartilage in a rat model of Kashin-Beck disease using T-2 toxin and selenium deficiency conditions. Rheumatol Int. 2013;33(1):157-166.

89. Chen J, Chu Y, Cao J, et al. Effects of T-2 toxin and selenium on chondrocyte expression of matrix metalloproteinases (MMP-1, MMP-13), alpha2-macroglobulin (alpha2M) and TIMPs. Toxicol In Vitro. 2011;25(2):492-499.

90. Yan D, Kang P, Li Y, et al. Radiographic findings of Wistar rats fed with T-2 toxin and Kashin-Beck disease-affected diet. Int J Rheum Dis. 2011;14(1):92-97.

91. Burk RF, Hill KE. Selenoprotein P: an extracellular protein with unique physical characteristics and a role in selenium homeostasis. Annu Rev Nutr. 2005;25:215-235.

92. Zagrodzki P, Szmigiel H, Ratajczak R, et al. The role of selenium in iodine metabolism in children with goiter. Environ Health Perspect. 2000;108(1):67-71.

93. Utiger RD. Kashin-Beck disease–expanding the spectrum of iodine-deficiency disorders. [comment]. N Engl J Med. 1998;339(16):1156-1158.

94. Jordan J, Fang F, Arab L, et al. Low selenium levels are associated with increased odds of radiographic knee and multijoint OA. Osteo & Cartilage. 2005;13(suppl A): S35.

95. Mathieu F, Begaux F, Lan ZY, et al. Clinical manifestations of Kashin-Beck disease in Nyemo Valley, Tibet. Int Orthop. 1997;21(3):151-156.

96. Wang Y, Yang Z, Gilula LA, et al. Kashin-Beck disease: radiographic appearance in the hands and wrists. Radiology. 1996;201(1):265-270.

97. Sokoloff L. Endemic forms of osteoarthritis. Clin Rheum Dis. 1985;11(2):187-202.

98. Hinsenkamp M, Ryppens F, Begaux F, et al. The anatomical distribution of radiological abnormalities in Kashin-Beck disease in Tibet. Int Orthop. 2001;25(3):142-146.

99. Hinsenkamp M, Mathieu F, Claus W, et al. Effects of physical environment on the evolution of Kashin-Beck disease in Tibet. Int Orthop. 2009;33(4):1085-1088.

100. Reed MH. Growth disturbances in the hands following thermal injuries in children. 2. Frostbite. Can Assoc Radiol J. 1988;39(2):95-99.

101. Yu W, Wang Y, Jiang Y, et al. Kashin-Beck disease in children: radiographic findings in the wrist. Skeletal Radiol. 2002;31(4):222-225.

102. Fu Q, Cao J, Renner JB, et al. Radiographic features of hand osteoarthritis in adult Kashin-Beck disease (KBD): the Yongshou KBD study. Osteoarthritis Cartilage. 2015;23(6):868-873.

103. Xiong G. Diagnostic, clinical and radiological characteristics of Kashin-Beck disease in Shaanxi Province, PR China. Int Orthop. 2001;25(3):147-150.

104. Fang H, Guo X, Farooq U, et al. Development and validation of a quality of life instrument for Kashin-Beck disease: an endemic osteoarthritis in China. Osteoarthritis Cartilage. 2012;20(7):630-637.

105. Oestreich AE. The acrophysis: a unifying concept for understanding enchondral bone growth and its

disorders. II. Abnormal growth. Skeletal Radiol. 2004;33(3):119-128.

106. Dong W, Zhang Y, Liu H, et al. Detection of unsaturated disaccharides, pyridinoline, and hydroxyproline in urine of patients with Kashin-Beck disease: comparison with controls in an endemic area. J Rheumatol. 2009;36(4):816-821.

107. Li XY, Guo X, Wang LX, et al. [Serum hyaluronic acid, tumor necrosis factor-alpha, vascular endothelial growth factor, NO, and Se levels in adult patients with Kashin-Beck disease]. Nan Fang Yi Ke Da Xue Xue Bao. 2007;27(7):941-944.

108. Cao J, Li S, Shi Z, et al. Articular cartilage metabolism in patients with Kashin-Beck disease: an endemic osteoarthropathy in China. Osteoarthritis Cartilage. 2008;16(6):680-688.

109. Tang X, Zhou Z, Shen B, et al. Serum levels of TNF-alpha, IL-1beta, COMP, and CTX-II in patients with Kashin-Beck disease in Sichuan, China. Rheumatol Int. 2012;32(11):3503-3509.

110. Shi X, Lv A, Ma J, et al. Investigation of MMP-1 genetic polymorphisms and protein expression and their effects on the risk of Kashin-Beck disease in the northwest Chinese Han population. J Orthop Surg Res. 2016;11(1):64.

111. Yang L, Liu H, Guo X, et al. The potential biochemical markers of Kashin-Beck disease: a meta-analysis. Biomarkers. 2016;21(7):633-638.

112. Wang S, Guo X, Tan WH, et al. Detection of serum proteomic changes and discovery of serum biomarkers for Kashin-Beck disease using surface-enhanced laser desorption ionization mass spectrometry (SELDI-TOF MS). J Bone Miner Metab. 2008;26(4):385-393.

113. Du J, Wu X, Zhang H, et al. Mass spectrometry-based proteomic analysis of Kashin-Beck disease. Mol Med Report. 2010;3(5):821-824.

114. Turan B, Balcik C, Akkas N. Effect of dietary selenium and vitamin E on the biomechanical properties of rabbit bones. Clin Rheumatol. 1997;16(5):441-449.

115. Wang SJ, Guo X, Zuo H, et al. Chondrocyte apoptosis and expression of Bcl-2, Bax, Fas, and iNOS in articular cartilage in patients with Kashin-Beck disease. J Rheumatol. 2006;33(3):615-619.

116. Pasteels JL, Liu FD, Hinsenkamp M, et al. Histology of Kashin-Beck lesions. Int Orthop. 2001;25(3):151-153.

117. Guo X, Zuo H, Cao CX, et al. Abnormal expression of Col X, PTHrP, TGF-beta, bFGF, and VEGF in cartilage with Kashin-Beck disease. J Bone Miner Metab. 2006;24(4):319-328.

118. Wang W, Guo X, Chen J, et al. Morphology and phenotype expression of types I, II, III, and X collagen and MMP-13 of chondrocytes cultured from articular cartilage of Kashin-Beck disease. J Rheumatol. 2008;35(4):696-702.

119. Moreno-Reyes R, Mathieu F, Boelaert M, et al. Selenium and iodine supplementation of rural Tibetan children affected by Kashin-Beck osteoarthropathy. Am J Clin Nutr. 2003;78(1):137-144.

120. Haubruge E, Chasseur C, Debouck C, et al. The prevalence of mycotoxins in Kashin-Beck disease. Int Orthop. 2001;25(3):159-161.

121. Sudre P, Mathieu F. Kashin-Beck disease: from etiology to prevention or from prevention to etiology? Int Orthop. 2001;25(3):175-179.

122. Shi Z, Cao J, Chen J, et al. Butenolide induced cytotoxicity by disturbing the prooxidant-antioxidant balance, and antioxidants partly quench in human chondrocytes. Toxicol In Vitro. 2009;23(1):99-104.

123. Yang L, Zhao GH, Yu FF, et al. Selenium and iodine levels in subjects with Kashin-Beck disease: a meta-analysis. Biol Trace Elem Res. 2016;170(1): 43-54.

124. Cheng AW, Bolognesi M, Kraus VB. DIO2 modifies inflammatory responses in chondrocytes. Osteoarthritis Cartilage. 2012;20(5):440-445.

125. Li SY, Cao JL, Shi ZL, et al. Promotion of the articular cartilage proteoglycan degradation by T-2 toxin and selenium protective effect. J Zhejiang Univ Sci B. 2008;9(1):22-33.

126. Cheng W, Stabler T, Bolognesi M, et al. Selenomethionine inhibits IL-1β induced nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX2) in primary human chondrocytes. Osteo Cartilage. 2009;17(suppl 1):S129.

127. Zhang F, Wen Y, Guo X, et al. Trans-omics pathway analysis suggests that eQTLs contribute to chondrocyte apoptosis of Kashin-Beck disease through regulating apoptosis pathway expression. Gene. 2014;553(2):166-169.

128. Zhai SS, Kimbrough RD, Meng B, et al. Kashin-Beck disease: a cross-sectional study in seven villages in the People’s Republic of China. J Toxicol Environ Health. 1990;30(4):239-259.

129. Chua KH, Aminuddin BS, Fuzina NH, et al. Insulin-transferrin-selenium prevent human chondrocyte dedifferentiation and promote the formation of high quality tissue engineered human hyaline cartilage. Eur Cell Mater. 2005;9:58-67, discussion 67.

130. Levander OA. Considerations in the design of selenium bioavailability studies. Fed Proc. 1983;42(6): 1721-1725.

131. Xia Y, Hill KE, Byrne DW, et al. Effectiveness of selenium supplements in a low-selenium area of China. Am J Clin Nutr. 2005;81(4):829-834.

132. Andriamanalijaona R, Kypriotou M, Bauge C, et al. Comparative effects of 2 antioxidants, selenomethionine and epigallocatechin-gallate, on catabolic and anabolic gene expression of articular chondrocytes. J Rheumatol. 2005;32(10):1958-1967.

133. Hodgson P, Hughes C, Day M, et al. Development of an in vitro culture system that mimics cartilage pathology in Kashin-Beck disease. Osteo & Cartilage. 2005; 13(suppl A):S164.

134. Hodgson P, Hughes C, Day C, et al. The effects of selenium and the fungal mycotoxin nivalenol on cartilage matrix metabolism: a culture system to mimic pathology in Kashin-Beck disease. Trans Orthop Res Soc. 2006;31:1413.

135. Peng A, Wang WH, Wang CX, et al. The role of humic substances in drinking water in Kashin-Beck disease in China. Environ Health Perspect. 1999;107(4): 293-296.

136. Yang C, Wolf E, Roser K, et al. Selenium deficiency and fulvic acid supplementation induces fibrosis of cartilage and disturbs subchondral ossification in knee joints of mice: an animal model study of Kashin-Beck disease. Virchows Arch A Pathol Anat Histopathol. 1993;423(6):483-491.

137. Ioannidis N, Kurz B, Hansen U, et al. Influence of fulvic acid on the collagen secretion of bovine chondrocytes in vitro. Cell Tissue Res. 1999;297(1):141-147.

138. Debouck C, Haubruge E, Bollaerts P, et al. Skeletal deformities induced by the intraperitoneal administration of deoxynivalenol (vomitoxin) in mice. Int Orthop. 2001;25(3):194-198.

139. Jianan T, Wenyu Z, Ribang L, et al. Geographic distribution of Kashin-Beck disease in China and the relation of ecological chemico-geography to its occurrence. In: Proceedings of the International Workshop on Kashin-Beck Disease and Non-communicable Diseases. Beijing: World Health Organization; 1990:12-26.

140. Jiayun D. The geographical distribution characteristics of Kashin-Beck disease in Sichuan province. In: Proceedings of the International Workshop on Kashin-Beck Disease and Non-communicable Diseases. Beijing: World Health Organization; 1990:27-30.

141. Shi XW, Guo X, Ren FL, et al. [Familial aggregation and sibling heritability in Kashin-Beck disease]. Nan Fang Yi Ke Da Xue Xue Bao. 2008;28(7):1187-1189.

142. Shi Y, Lu F, Liu X, et al. Genetic variants in the HLA-DRB1 gene are associated with Kashin-Beck disease in the Tibetan population. Arthritis Rheum. 2011;63(11):3408-3416.

143. Yang Z, Xu Y, Luo H, et al. Whole-exome sequencing for the identification of susceptibility genes of Kashin-Beck disease. PLoS ONE. 2014;9(4):e92298.

144. Zhao QM, Guo X, Lai JH, et al. Association of TNF-alpha and Fas gene promoter polymorphism with the risk of Kashin-Beck disease in Northwest Chinese population. Clin Rheumatol. 2012;31(7):1051-1057.

145. Zhang F, Guo X, Zhang Y, et al. Genome-wide copy number variation study and gene expression analysis identify ABI3BP as a susceptibility gene for Kashin-Beck disease. Hum Genet. 2014;133(6):793-799.

146. Xiong YM, Mo XY, Zou XZ, et al. Association study between polymorphisms in selenoprotein genes and susceptibility to Kashin-Beck disease. Osteoarthritis Cartilage. 2010;18(6):817-824.


147. Du XH, Dai XX, Xia Song R, et al. SNP and mRNA expression for glutathione peroxidase 4 in Kashin-Beck disease. Br J Nutr. 2012;107(2):164-169.

148. Wen Y, Zhang F, Li C, et al. Gene expression analysis suggests bone development-related genes GDF5 and DIO2 are involved in the development of Kashin-Beck disease in children rather than adults. PLoS ONE. 2014;9(7):e103618.

149. Yang L, Zhao GH, Liu H, et al. Field synopsis and meta-analyses of genetic epidemiological evidence for Kashin-Beck disease, an endemic osteoarthropathy in China. Mol Genet Genomics. 2016;291(5):1823-1833.

150. Wen Y, Hao J, Xiao X, et al. PPARGC1B gene is associated with Kashin-Beck disease in Han Chinese. Funct Integr Genomics. 2016;16(4):459-463.

151. Zhang F, Dai L, Lin W, et al. Exome sequencing identified FGF12 as a novel candidate gene for Kashin-Beck disease. Funct Integr Genomics. 2016;16(1):13-17.

152. Hao J, Wang W, Wen Y, et al. A bivariate genome-wide association study identifies ADAM12 as a novel susceptibility gene for Kashin-Beck disease. Sci Rep. 2016;6:31792.

153. Yang C, Niu C, Bodo M, et al. Fulvic acid supplementation and selenium deficiency disturb the structural integrity of mouse skeletal tissue. An animal model to study the molecular defects of Kashin-Beck disease. Biochem J. 1993;289(Pt 3):829-835.

154. Moreno-Reyes R, Egrise D, Neve J, et al. Selenium deficiency-induced growth retardation is associated with an impaired bone metabolism and osteopenia. J Bone Miner Res. 2001;16(8):1556-1563.

155. Sasaki S, Iwata H, Ishiguro N, et al. Low-selenium diet, bone, and articular cartilage in rats. Nutrition. 1994;10(6):538-543.

156. Ren FL, Guo X, Zhang RJ, et al. Effects of selenium and iodine deficiency on bone, cartilage growth plate and chondrocyte differentiation in two generations of rats. Osteoarthritis Cartilage. 2007;15(10):1171-1177.

157. Guanghou N, Baozhen Z, Yupie Z, et al. Studies on the bacteria toxin etiology of Kashin-Beck disease. In: Proceedings of the International Workshop on Kashin-Beck Disease and Non-communicable Diseases. Beijing: World Health Organization; 1990.

158. Zhou X, Yang H, Guan F, et al. T-2 toxin alters the levels of collagen II and its regulatory enzymes MMPs/TIMP-1 in a low-selenium rat model of Kashin-Beck disease. Biol Trace Elem Res. 2016;169(2):237-246.

159. Kurz B, Jost B, Schunke M. Dietary vitamins and selenium diminish the development of mechanically induced osteoarthritis and increase the expression of antioxidative enzymes in the knee joint of STR/1N mice. Osteoarthritis Cartilage. 2002;10(2):119-126.

160. Downey CM, Horton CR, Carlson BA, et al. Osteo-chondroprogenitor-specific deletion of the selenocysteine tRNA gene, Trsp, leads to chondronecrosis and abnormal skeletal development: a putative model for Kashin-Beck disease. PLoS Genet. 2009;5(8):e1000616.

161. Kohrle J, Brigelius-Flohe R, Bock A, et al. Selenium in biology: facts and medical perspectives. Biol Chem. 2000;381(9-10):849-864.

162. Yu FF, Han J, Wang X, et al. Salt-rich selenium for prevention and control children with Kashin-Beck

disease: a meta-analysis of community-based trial. Biol Trace Elem Res. 2016;170(1):25-32.

163. Yang GQ, Xia YM. Studies on human dietary requirements and safe range of dietary intakes of selenium in China and their application in the prevention of related endemic diseases. Biomed Environ Sci. 1995;8(3):187-201.

164. EPA. Selenium and Compounds (CASRN 7782-49-2). In: Integrated Risk Information System; 2006.

165. Mathieu F, Suetens C, Begaux F, et al. Effects of physical therapy on patients with Kashin-Beck disease in Tibet. Int Orthop. 2001;25(3):191-193.

166. Liu W, Liu G, Pei F, et al. Kashin-Beck disease in Sichuan, China: report of a pilot open therapeutic trial. J Clin Rheumatol. 2012;18(1):8-14.

167. Tang X, Pei FX, Zhou ZK, et al. A randomized, single-blind comparison of the efficacy and tolerability of hyaluronate acid and meloxicam in adult patients with Kashin-Beck disease of the knee. Clin Rheumatol. 2012;31(7):1079-1086.

168. Luo R, Liu G, Liu W, et al. Efficacy of celecoxib, meloxicam and paracetamol in elderly Kashin-Beck disease (KBD) patients. Int Orthop. 2011;35(9):1409-1414.

169. Liu FD, Wang ZL. Hinsenkamp M. Osteotomy at the knee for advanced cases of Kashin-Beck disease. Int Orthop. 1998;22(2):87-91.

170. Stone R. A medical mystery in middle China. Science. 2009;324.

171. Anonymous. Diagnostic criteria of Kaschin Beck disease. Beijing, China: Ministry of Public Health Beijing; 1995.

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